This invention relates to a shift control arrangement in a multi-speed transmission. In particular, it relates to a means for preventing inadvertent selection of a reverse direction while a high gear ratio has been selected. The control system envisioned operates with two levers, one lever is operable through a gating plate to select the direction, while the second lever is operable through a similar gating plate to select the speed.
In multi-speed transmissions, particularly those associated with construction equipment, it is known to provide several speeds in both forward and reverse operation while providing additional speeds in the forward range only. The additional forward range speeds are usually provided through the higher gear ratios and are selectable by the operator through a single speed control lever. Systems are available wherein selection of a reverse mode at the higher gear ratios is possible at the shift lever, while actual engagement is prevented due to interlocking means in the transmission. That is to say, an inexperienced operator in a heavy construction vehicle could shift from the forward to the reverse mode while operating in the high gear ratio expecting the transmission to shift, while in reality the transmission is constructed so that such a shift does not occur. It should be readily apparent that this condition could be detrimental to operation of the vehicle. Similarly, an inexperienced operator could place the transmission controls in the higher gear ratios and select a reverse direction before starting and find the vehicle will only operate in the forward direction.
It is, therefore, appropriate to provide a means to prevent an inexperienced operator from selecting a reverse direction while the vehicle is operating in the higher gear ratio to correspond to the already limited transmission which will not engage the reverse direction in the higher gear ratio.